I'm looking to get some evidence for a business plan, I am about to start writing about how much a web site can make from google ads but I cannot find anything to base this on.

I know that this is a very difficult thing to prove and it depends on renders, click throughs, how close the ads are to the content of the site and how much the users are liable to click through. But I really need to put something on paper with some evidence.

Does anyone know of any sites or documents that might give me some detail that I can use. The site is strongly forum based and I expect there to be 25-50 million page renders per month.

Thanks